S1 pinout

Nine connectors, all on the top side. Hover a connector on the map to name its pins, or select it to jump to its table. Pin 1 is the square pad.

• Power
• Ground
• Motor
• Bus / data
• Input
• Debug
• Not connected
• Shaft centre (encoder chip on the underside)

Top view, to scale (38 × 38 mm). Hover or tap a connector to name its pins; select it for the full pinout.

3.3 V logic

The step/dir, switch and external encoder signals go straight to the microcontroller. They take 3.3 V logic only: 5 V signals need a level shifter. See Wiring.

Power (J1)

On the board

J1 2-pin screw terminal, 3.5 mm pitch

Mates with

0.5–1.0 mm² (20–18 AWG) wire with ferrules

Motor and logic supply, 12–28 V DC. The board makes its own 5 V and 3.3 V.

Pin	Signal	Type	Function
1	GND	Ground	Supply return.
2	VIN	Power	12–28 V DC. Never above 28 V.

Motor (J8)

On the board

J8 4-pin screw terminal, 2.54 mm pitch

Mates with

0.25–0.5 mm² (24–20 AWG) wire with ferrules

The two coils of a bipolar stepper. A1/A2 is one coil, B1/B2 the other.

Pin	Signal	Type	Function
1	B2	Motor	Coil B, second end.
2	B1	Motor	Coil B, first end.
3	A2	Motor	Coil A, second end.
4	A1	Motor	Coil A, first end.

CAN (J4)

On the board

J4 4-pin screw terminal, 2.54 mm pitch

Mates with

Twisted pair, 0.25–0.5 mm² with ferrules

The CAN-FD bus. Connects to the Tercio FD and to the other drivers.

Pin	Signal	Type	Function
1	NC	Not connected	Not connected. Leave empty.
2	GND	Ground	Bus ground reference. Connect it to the adapter’s GND.
3	CAN-H	Bus / data	CAN high.
4	CAN-L	Bus / data	CAN low.

Termination (J9)

On the board

J9 2-pin header, 2.54 mm pitch

Mates with

2.54 mm jumper

Bus termination. Fit the jumper only on the driver at the far end of the bus.

Pin	Signal	Type	Function
1	CAN-H	Bus / data	Bus high.
2	TERM	Bus / data	120 Ω to CAN-L.

Inputs (J7)

On the board

J7 4-pin screw terminal, 2.54 mm pitch

Mates with

0.25–0.5 mm² wire with ferrules

Two switch inputs for limit or home switches, with 3.3 V and GND to power a sensor.

Pin	Signal	Type	Function	MCU
1	+3.3V	Power	3.3 V out for a switch or sensor, 50 mA at most.	—
2	GND	Ground	Ground.	—
3	IN1	Input	Negative limit / home switch. 3.3 V logic.	PB12
4	IN2	Input	Positive limit / home switch. 3.3 V logic.	PB13

Step/dir (J5)

On the board

J5 JST PH, 5-pin side entry (S5B-PH-K-S), 2.0 mm pitch

Mates with

JST PHR-5 housing with SPH-002T-P0.5S crimps

Take motion commands from a step/dir controller while the loop stays closed. 3.3 V logic only.

Pin	Signal	Type	Function	MCU
1	NC	Not connected	Not connected.	—
2	EN	Input	Enable. Active low by default (pulled up on board).	PA0
3	STEP	Input	One step per rising edge.	PA1
4	DIR	Input	High = positive direction. Pulled down on board.	PA2
5	GND	Ground	Signal ground. Connect it to the controller’s ground.	—

External encoder (J2)

Pins are numbered in two rows: odd numbers along the row nearer the board centre, even numbers along the edge.

On the board

J2 JST PHD, 2 × 6 (12-pin), 2.0 mm pitch

Mates with

JST PHDR-12VS housing with SPHD-002T-P0.5 crimps

For an encoder away from the board: AS5048A over SPI or AS5600 over I²C. 3.3 V only.

Pin	Signal	Type	Function	MCU
1	+3.3V	Power	Encoder supply.	—
2	SDA	Bus / data	I²C data (AS5600).	PA8
3	GND	Ground	Ground.	—
4	SCL	Bus / data	I²C clock (AS5600).	PA9
5	NC	Not connected	Not connected.	—
6	CS	Bus / data	SPI chip select (AS5048A).	PB2
7	NC	Not connected	Not connected.	—
8	MISO	Bus / data	SPI data from the encoder.	PA6
9	GND	Ground	Ground.	—
10	MOSI	Bus / data	SPI data to the encoder.	PA7
11	+3.3V	Power	Encoder supply.	—
12	SCK	Bus / data	SPI clock.	PA5

SWD (J3)

On the board

J3 5-pin header, 2.54 mm pitch

Mates with

ST-Link or any SWD probe (same order as the Tercio FD)

Programming and debugging. Only needed to flash firmware.

Pin	Signal	Type	Function	MCU
1	+3.3V	Power	Target voltage sense for the probe. Do not power the board from here.	—
2	SWDIO	Debug	Serial wire data.	PA13
3	SWCLK	Debug	Serial wire clock.	PA14
4	NRST	Debug	Reset, active low.	—
5	GND	Ground	Ground.	—

Boot (J6)

On the board

J6 3-pin header, 2.54 mm pitch

Mates with

2.54 mm jumper

Leave open. A jumper on pins 1–2 starts ST’s ROM bootloader instead of the firmware (recovery only).

Pin	Signal	Type	Function
1	+3.3V	Power	Jumper to pin 2 to enter the bootloader.
2	BOOT0	Input	Pulled low on board: normal start.
3	GND	Ground	Ground.

LED

LED	Colour	Meaning
D1, PWR	Red	The board is powered.

The S1 has no status LED: its state is in telemetry, and Tercio Control shows it on every motor’s page.

Mounting holes

Four 3.2 mm holes for M3 screws, centres 30.6 × 30.65 mm. The encoder chip is exactly at the centre of the four holes, so anything that centres the board on the holes centres the encoder on the shaft. See Mounting.